This invention relates to IC card systems using IC cards containing integrated circuits and card terminals which act together to perform transactions.
The recent years have been called the "cashless era," by using "plastic money" issued by credit companies, oil companies, department stores, etc., the purchase of goods without any handling of cash has been possible. Up to now, plastic cards, embossed cards, and magnetic stripe cards have generally been used, but these cards are easy to forge, and their misuse has been problematic. To solve this problem, an IC circuit in which a personal identification number is stored is provided within the card, and it has been specifically developed because that personal identification number cannot be easily read from the IC card. This IC card is advantageous in that it is difficult to duplicate, its secrecy maintenance capability is excellent, and it can store a great amount of data. Since the personal identification number is input directly by the card user, other persons, for example, a bank clerk, cannot find out the personal identification number. In this respect, the card has a very high security factor.
However, since the physical shape and dimensions, and connection terminals of such an IC card are standardized by the I.S.O., it is possible that cards even with many different kinds of internal circuit configurations may be connected to the same card terminal. However, since the circuit configurations or the performance of component devices of the cards will differ, the operating conditions will naturally also differ. Therefore, in the case of a terminal of the type which supplies power to the card when it is coupled with the card, it is necessary to set the operating energy level according to the operating conditions of each card in order to obtain the maximum operatability from each card. Especially, the cards developed lately have ever increasing high-performance capabilities due to progressive engineering. A configuration of the terminal which can perform an immediate exchange of data from either new high-performance cards or older cards will be necessary.
One example of a high performance capability in an IC card is the improvements in data writing and storage of important personal identification numbers. In this case, on the terminal side, variations in the data write voltages and current tolerances in the improved IC cards that are issued must be coped with.
In addition to the write voltage and current for the memory in the IC card, items to be considered for obtaining compatibility with the terminal are things such as: the maximum data transmission capacity of the IC card, the signal response time from an instant that the IC card receives a signal till it transmits a response signal, and an application time of the write voltage.